I thought they raised the chance for unique items during the final beta.
I'm on day 220 now - the 2nd crisis, greenskins, has just started - and I never found a unique at a location or saw one in the hands of a bandit leader or hedgeknight. I don't even think there were more than a dozen for sale - weaponsmith, armorer and fletcher combined - and travelling from shop to shop is basically all I'm doing atm.
What is the state of the town itself? I've only gotten uniques in towns that are well stocked. If they have been raided/sieged and barely have anything for sale, it seems that the chance for unique is minuscule.